Re: net/sched/sch_fq.c:966:12: warning: stack frame size of 1400 bytes in function 'fq_dump'

From: Eric Dumazet
Date: Mon Jun 15 2020 - 12:17:41 EST

On Sun, Jun 14, 2020 at 11:26 PM kernel test robot <lkp@xxxxxxxxx> wrote:
>
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 96144c58abe7ff767e754b5b80995f7b8846d49b
> commit: 39d010504e6b4485d7ceee167743620dd33f4417 net_sched: sch_fq: add horizon attribute
> date: 6 weeks ago
> :::::: branch date: 3 hours ago
> :::::: commit date: 6 weeks ago
> config: arm-randconfig-r006-20200614 (attached as .config)
> compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project c669a1ed6386d57a75a602b53266466dae1e1d84)
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # install arm cross compiling tool for clang build
> # apt-get install binutils-arm-linux-gnueabi
> git checkout 39d010504e6b4485d7ceee167743620dd33f4417
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>
> All warnings (new ones prefixed by >>, old ones prefixed by <<):
>
> >> net/sched/sch_fq.c:966:12: warning: stack frame size of 1400 bytes in function 'fq_dump' [-Wframe-larger-than=]
> static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
> ^


This looks like a bug in CLANG on ARM, there is no way fq_dump() could
consume so much stack space.



> 1 warning generated.
>
> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=39d010504e6b4485d7ceee167743620dd33f4417
> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> git remote update linus
> git checkout 39d010504e6b4485d7ceee167743620dd33f4417
> vim +/fq_dump +966 net/sched/sch_fq.c
>
> afe4fd062416b1 Eric Dumazet 2013-08-29 965
> afe4fd062416b1 Eric Dumazet 2013-08-29 @966 static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
> afe4fd062416b1 Eric Dumazet 2013-08-29 967 {
> afe4fd062416b1 Eric Dumazet 2013-08-29 968 struct fq_sched_data *q = qdisc_priv(sch);
> 48872c11b77271 Eric Dumazet 2018-11-11 969 u64 ce_threshold = q->ce_threshold;
> 39d010504e6b44 Eric Dumazet 2020-05-01 970 u64 horizon = q->horizon;
> afe4fd062416b1 Eric Dumazet 2013-08-29 971 struct nlattr *opts;
> afe4fd062416b1 Eric Dumazet 2013-08-29 972
> ae0be8de9a53cd Michal Kubecek 2019-04-26 973 opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
> afe4fd062416b1 Eric Dumazet 2013-08-29 974 if (opts == NULL)
> afe4fd062416b1 Eric Dumazet 2013-08-29 975 goto nla_put_failure;
> afe4fd062416b1 Eric Dumazet 2013-08-29 976
> 65c5189a2b57b9 Eric Dumazet 2013-11-15 977 /* TCA_FQ_FLOW_DEFAULT_RATE is not used anymore */
> 65c5189a2b57b9 Eric Dumazet 2013-11-15 978
> 48872c11b77271 Eric Dumazet 2018-11-11 979 do_div(ce_threshold, NSEC_PER_USEC);
> 39d010504e6b44 Eric Dumazet 2020-05-01 980 do_div(horizon, NSEC_PER_USEC);
> 48872c11b77271 Eric Dumazet 2018-11-11 981
> afe4fd062416b1 Eric Dumazet 2013-08-29 982 if (nla_put_u32(skb, TCA_FQ_PLIMIT, sch->limit) ||
> afe4fd062416b1 Eric Dumazet 2013-08-29 983 nla_put_u32(skb, TCA_FQ_FLOW_PLIMIT, q->flow_plimit) ||
> afe4fd062416b1 Eric Dumazet 2013-08-29 984 nla_put_u32(skb, TCA_FQ_QUANTUM, q->quantum) ||
> afe4fd062416b1 Eric Dumazet 2013-08-29 985 nla_put_u32(skb, TCA_FQ_INITIAL_QUANTUM, q->initial_quantum) ||
> afe4fd062416b1 Eric Dumazet 2013-08-29 986 nla_put_u32(skb, TCA_FQ_RATE_ENABLE, q->rate_enable) ||
> 76a9ebe811fb3d Eric Dumazet 2018-10-15 987 nla_put_u32(skb, TCA_FQ_FLOW_MAX_RATE,
> 76a9ebe811fb3d Eric Dumazet 2018-10-15 988 min_t(unsigned long, q->flow_max_rate, ~0U)) ||
> f52ed89971adbe Eric Dumazet 2013-11-15 989 nla_put_u32(skb, TCA_FQ_FLOW_REFILL_DELAY,
> f52ed89971adbe Eric Dumazet 2013-11-15 990 jiffies_to_usecs(q->flow_refill_delay)) ||
> 06eb395fa9856b Eric Dumazet 2015-02-04 991 nla_put_u32(skb, TCA_FQ_ORPHAN_MASK, q->orphan_mask) ||
> 77879147a3481b Eric Dumazet 2016-09-19 992 nla_put_u32(skb, TCA_FQ_LOW_RATE_THRESHOLD,
> 77879147a3481b Eric Dumazet 2016-09-19 993 q->low_rate_threshold) ||
> 48872c11b77271 Eric Dumazet 2018-11-11 994 nla_put_u32(skb, TCA_FQ_CE_THRESHOLD, (u32)ce_threshold) ||
> 583396f4ca4d6e Eric Dumazet 2020-03-16 995 nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log) ||
> 39d010504e6b44 Eric Dumazet 2020-05-01 996 nla_put_u32(skb, TCA_FQ_TIMER_SLACK, q->timer_slack) ||
> 39d010504e6b44 Eric Dumazet 2020-05-01 997 nla_put_u32(skb, TCA_FQ_HORIZON, (u32)horizon) ||
> 39d010504e6b44 Eric Dumazet 2020-05-01 998 nla_put_u8(skb, TCA_FQ_HORIZON_DROP, q->horizon_drop))
> afe4fd062416b1 Eric Dumazet 2013-08-29 999 goto nla_put_failure;
> afe4fd062416b1 Eric Dumazet 2013-08-29 1000
> d59b7d8059ddc4 Yang Yingliang 2014-03-12 1001 return nla_nest_end(skb, opts);
> afe4fd062416b1 Eric Dumazet 2013-08-29 1002
> afe4fd062416b1 Eric Dumazet 2013-08-29 1003 nla_put_failure:
> afe4fd062416b1 Eric Dumazet 2013-08-29 1004 return -1;
> afe4fd062416b1 Eric Dumazet 2013-08-29 1005 }
> afe4fd062416b1 Eric Dumazet 2013-08-29 1006
>
> :::::: The code at line 966 was first introduced by commit
> :::::: afe4fd062416b158a8a8538b23adc1930a9b88dc pkt_sched: fq: Fair Queue packet scheduler
>
> :::::: TO: Eric Dumazet <edumazet@xxxxxxxxxx>
> :::::: CC: David S. Miller <davem@xxxxxxxxxxxxx>
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
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